1. Field of the Invention
The invention relates to methods for manufacturing field emission cathodes and, particularly, to a method for manufacturing a field emission cathode including a carbon nanotube array.
2. Discussion of Related Art
Carbon nanotubes (CNTs) produced by means of arc discharge between graphite rods were first discovered and reported in an article by Sumio Iijima, entitled “Helical Microtubules of Graphitic Carbon” (Nature, Vol. 354, Nov. 7, 1991, pp. 56-58). Carbon nanotubes are electrically conductive along their length, are chemically stable, and can have, individually, very small diameters (much less than 100 nanometers) and large aspect ratios (length/diameter). Due to these and other properties, it has been suggested that carbon nanotubes can play an important role in fields such as microscopic electronics, field emission devices, thermal interface materials, etc.
Generally, a CNT field emission device includes a field emission cathode, and the field emission cathode includes a conductive electrode and a carbon nanotube array formed on the conductive electrode. The method for manufacturing the field emission cathode mainly includes the following steps: firstly, providing a silicon or silicon dioxide substrate; secondly, forming a conductive electrode on the substrate; thirdly, forming a catalyst layer on the conductive electrode; fourthly, heating the substrate with the catalyst layer formed thereon in air at a temperature in the approximate range from 300° C. to 500° C. for 10 minutes to 12 hours, then annealing the substrate to obtaining catalyst particles; fifthly, placing the substrate with the catalyst particles disposed thereon in a reaction device, introducing a protection gas thereinto, and heating the substrate to a temperature in the approximate range from 400° C. to 750° C.; and introducing a reaction gas into the reaction device for 0.5 minutes to 2 hours to grow a carbon nanotube array on the substrate.
As the field emission cathode is used, an insulative layer can, beneficially, be adopted/incorporated among adjacent carbon nanotubes to avoid the electromagnetic shielding among the carbon nanotubes. However, the typical method for manufacturing the insulative layer is relatively complex and, thus, is not fit for mass production. Furthermore, the toughness and pliability of the field emission cathode is relatively poor and is generally not fit for flexible display devices.
What is needed, therefore, is a method for manufacturing a field emission cathode which includes an electrode and an insulating film incorporated therewith. What is further needed is a field emission cathode that is fit for flexible display devices. Furthermore, what is needed is a method for producing such that is relatively easy and that can be used in mass production.